==== Front Ann Saudi MedAnn Saudi MedAnnals of Saudi Medicine0256-49470975-4466King Faisal Specialist Hospital and Research Centre 2418894510.5144/0256-4947.2013.492asm-5-492Case ReportClear cell myoepithelioma of the hard palate Hakeem Arsheed Hussain aHazarika Biswajyoti bHakeem Imtiyaz Hussain c a Surgical Oncology, Prince Aly Khan Hospital, Nesbit Road, Mazagaon, Mumbai, Maharashtra, India b Surgical Oncology, Max Cancer Centre, Saket, New Delhi, India c Internal Medicine, Florida Hospital Medical Center, Winter Park Orlando, Florida, USACorrespondence: Arsheed Hussain Hakeem, MD, Nesbit Road, Mazagaon, Mumbai 400010 Maharashtra, India, T: +91-9920226332, F: (91-22) 25763344/3311, drahhakim@gmail.comSep-Oct 2013 33 5 492 494 Copyright © 2013, Annals of Saudi Medicine2013This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.Clear cell myoepithelioma arising from the minor salivary glands of hard palate is a rare entity. Most of the cases of palatal myoepitheliomas reported so far are either plasmacytoid or spindle cell type. Our literature search revealed only one case report of clear cell myoepithelioma of the palate. We report a case in a 21-year-old female who presented to us with a non-ulcerating, painless firm swelling of the left side of the hard palate. The tumor was excised with a healthy rim of surrounding tissue. Immunohistochemistry was performed on formalin-fixed and paraffin-embedded tissue with a panel of immunohistochemical markers. Tumor cells showed positivity for S100, cytokeratin and Muscle specific actin. Histological and immunohistochemical analyses revealed the tumor to be a myoepithelioma of the clear cell variety. ==== Body Myoepitheliomas are very rare tumurs of the salivary glands constituting less than 1.5% of all salivary gland tumors.1 The most common site of occurrence is the parotid gland.1–3 Although, clear cell myoepitheliomas have been reported at the other sites, most of the cases of palatal myoepitheliomas reported are either of the plasmacytoid or spindle cell type.4 A review of published reports revealed only one case of clear cell myoepithelioma of the hard palate reported by Agarwal et al. 5 The extreme rarity of clear cell myoepithelioma of the hard palate prompted us to report this case with the objective of contributing to a better understanding of this neoplasm. We discuss the clinical, radiological and pathological characteristics. CASE A 21-year-old female was referred to the Head and Neck Unit at Prince Aly Khan hospital, Department of Surgical Oncology, with recurrent painless swelling of the hard palate. She had undergone excision of the a similar swelling in the same region 4 months previously in another facility. Histopathological analysis of the previous surgical specimen showed it to be clear cell myoepithelioma. There was history of a progressive but slow increase in the size of this recurrent swelling. On intraoral examination there was smooth, fleshy, firm mass on left side of the hard palate approximately 3×3 cm in size (Figure 1). CT scan of the paranasal sinuses showed a well defined lobulated enhancing soft tissue mass, 3.4×2.5 cm in the transverse plane causing expansion of the left maxillary sinus. Erosion of the medial wall and floor of the maxillary sinus, including a portion of the maxillary alveolar process (in the molar region), was also noted. Mild focal erosion of the posterior wall of the left maxillary sinus was also seen without extension of the soft tissue into the masticator space. Widening of the ptery-go- palatine fissure was also noted on CT scan with the presence of enhancing soft tissue within it (Figure 2). With these observations and previous histopathology, a diagnosis of recurrent/residual clear cell myoepithelioma was made. An enbloc infrastructure maxillectomy was done with adequate margins. Histpathological examination of the surgical specimen showed grossly infiltrative fleshy white circumscribed mass measuring 3.8×3.7×2 cm with adequate cut margins. The overlying mucosa was opaque, white and smooth. The tumor was composed of large polyhedral cells with clear eosinophilic cytoplasm and these cells were arranged in closely packed interlacing bundles. The nuclei were round to oval, eccentrically placed and were vesicular with small nucleoli (Figures 3, 4). Immunohistochemically, the clear cells were immunoreactive for cytokeratin, S-100 and muscle-specific actin (MSA). A diagnosis of clear cell type myoepithelioma of minor salivary gland origin was made on microscopy and tumor was invasive in nature. The postoperative period was uneventful. Since she had a recurrence and the tumor was invasive in nature, adjuvant treatment of postoperative adjuvant radiotherapy was also given to the primary site. After 3 years of follow up she was free of disease without any signs of recurrence. DISCUSSION Myoepitheliomas are rare benign tumors, with the parotid gland and palate accounting for three-fourths of all cases.6 The plasmacytoid variant is usually seen on the palate in slightly younger individuals, while the spindle cell type tends to occur in the parotid gland of older individuals.7,8 Clear cell tumors of the salivary glands are almost invariably malignant in nature, with rare exceptions in the form of myoepitheliomas and oncocytomas.8 Our literature search revealed only one case of clear cell myoepithelioma of the hard palate reported by Agarwal et al.5 In our review, 20 cases of ultrastructurally or immunohistochemically confirmed myoepithelioma of the palatal minor salivary gland were found (Table 1). Of the 20 cases of palatal myoepitheliomas reported, 17 cases were of the plasmacytoid cell type, two were of the clear cell type, one belonged to the spindle cell variety and one was of mixed cellularity. Electron microscopic and immunohistochemical examinations are useful for accurate identification and characterization of myoepithelial cells. Immunohistochemically, a large number of markers have been used for establishing the diagnosis of myoepitheliomas. The myoepithelial cells are usually found to be immunoreactive to S-100, actin and prekeratin, and are nonreactive to desmin and EMA. Other markers that have been used in some reports are CEA, secretory piece, high molecular weight keratin, cytokeratin and factor VIII antigen.4 The reactivity to MSA and vimentin has been reported variably in different reports.6,10–12 In our patient, the tumor cells were found to be immunoreactive to MSA, S-100 and cytokeratin and negative for vimentin and EMA. In conclusion, myoepitheliomas are rare benign tumors arising from minor and major salivary glands. Immunohistochemical staining is extremely important for diagnosis. The clear cell variants of myoepitheliomas are extremely rare on the palate with only one case reported. Adequate excision with clear margins is usually curative. Figure 1 Clinical picture showing the smooth swelling on the left side of the hard palate. Figure 2 CT scan axial view showing the well-defined lobulated mass eroding the palate with extension into the maxillary antrum. Figure 3 Photomicrograph under low power showing sheets and cords of ovoid to spindle component with moderate amount of pale to eosinophilic cytoplasm (hematoxylin-eosin stain ×100). Figure 4 Photomicrograph under high power showing ovoid to spindle cells with uniform, mildly hyperchromatic nuclei and inconspicuous nucleolei (hematoxylin-eosin stain ×100). Table 1 Reported cases of myoepithelioma of minor salivary gland tumor of palate. Report Age/Sex Site Cell type Kahn and Schoub9 17/F Hard palate Plasmacytoid Luna et al10 30/F Hard palate Spindle Sciubba and Goldstein1 22/M palate Plasmacytoid Nesland et al11 18/F Soft palate Plasmacytoid Barnes et al6 24/F Hard palate Plasmacytoid Enomoto et al12 57/F Soft palate Plasmacytoid Ellyn and Gnepp13 8/F Soft palate Plasmacytoid Kawabe et al14 53/M Soft palate Plasmacytoid Stromeyer et al15 14/M Anterior maxilla Cytological pleomorphism Harusachi et al16 42/F Hard palate Plasmacytoid Agarwal et al5 40/F Hard palate Clear cell type Rastogi et al17 33/M Hard palate Plamacytoid Lins JE et al18 8/F Soft palate Plasmacytoid Lopez JI et al19 46/M Soft palate Plasmacytoid Acikalin MF et al20 32/M Soft palate Plasmacytoid Zelaya et al21 28/F Hard palate Plasmacytoid Kanazawa H et al4 42/F Hard palate Plasmacytoid Katsuyama E et al22 67/F Soft palate Plasmacytoid Nwoku et al23 11/M Palate Plasmacytoid Present case 21/F Hard palate Clear cell type ==== Refs REFERENCES 1 Sciubba JJ Brannon RB Myoepithelioma of salivary glands: Report of 23 cases Cancer 1982 49 280 2 Neville BW Oral & MaxilIofacial Pathology Philadelphia, PA Saunders 2001 413 3 Seifert G Histological Typing of Salivary Gland Tumors ed 2 World Health Organization International Histological classification of Tumors Berlin, Germany Springer-Vet-lag 1991 12 4 Kanazawa H Furuya T Watanabe T Kato J Plasmacytoid myoepithelioma of the palate J Oral Maxillofac Surg 1999 57 857 60 10416636 5 Agarwal AK Sethi A Chopra S Sareen D Clear cell myoepithelioma of the hard palate Braz J Oral Sci 2007 6 23 1467 1469 6 Barnes L Appel BN Perez H El-Attar AM Myoepitheliomas of the head and neck: case report and review J Surg Oncol 1985 28 21 8 2982059 7 De Stefani A Lerda W Bussi M Valente G Cortesina G Tumours of the parapharyngeal space: case report of clear cell myoepithelioma of the parotid gland and review of literature Acta Otolaryngol Ital 1999 19 276 82 8 Maiorano E Altini M Favia G Clear cell tumors of the salivary glands, jaws and oral mucosa Semin Diagn Pathol 1997 14 203 12 9279976 9 Kahn LB Schoub L Myoepithelioma of the palate: histochemical and ultrastructural observations Arch Pathol 1973 95 209 211 4346850 10 Luna MA Mackay B Games-Araujo J Myoepithelioma of the palate: Report of a case with histochemical and electron microscopic observation Cancer 1973 32 1429 4357077 11 Nesland JM Olafsson J Sobrinho-Simoes M Plasmacytoid myoepithelioma of the palate J Oral Pathol 1981 10 14 21 6259307 12 Enomoto T Hori M Miyake M So called myoepithelioma of the soft palate: Report of a case Jpn J Oral Maxillofac Surg 1985 31 351 13 Ellyn JEW Gnepp DR Myoepithelioma of the palate in a child Int J Pediatr Otorhinolaryngol 1986 11 5 2423468 14 Kawabe R Masuda G Horimoto S Plasmacytoid myoepithelioma ofminor salivary gland origin: A case report of the soft palate and review of the literature Jpn J Oral Maxillofac Surg 1991 37 1055 15 Stromeyer FW Haggitt RC Nelson JF Myoepithelioma of minor salivary gland origin: light and electronmicroscopical study Arch Pathol 1975 99 242 48374 16 Harusachi K Takanori F Toshihide W J Oral Maxillofac Surg 1999 57 857 10416636 17 Rastogi S Modi M Dhawan V Myoepithelioma of palate. 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